Week 3 Improvement of the designed circuit

After the failure of the circuit design, which cannot output even a whole output waveform all times though the simulation can output a wrong wave, we attempted to change components and structures of the design. After analysis with the tutor and the technical assistance, the main possible reasons can be summarized as below. Firstly, the function of the comparator was not effective as we hope. The connection of it might be wrong. Secondly, the input A of the oscilloscope represents to the input wave and it was normal. However the input B cannot conduct an output. The input B equals to the output of the amplifier. So the function of the amplifier which connected to the oscilloscope needs to be checked. Thirdly, the results of the simulation and the real circuit on the breadboard were different. Change another breadboard and close up the circuit might help. After that, the input voltage we designed seemed to be so high. The gain of the amplifier is (R4+R5)/R5 , so the gain should be near 100. The amplified voltage needs to under the power supply. Reduce the input voltage to 20mV or 30mV would be fine. At last but not the least important, the filter of the PIR sensor could help its sensitivity. The two pictures below showed the test of the first amplifier without the comparator and its simulated output.

The completeness of the system got a basic guarantee. However, the amplitude of the gain is too small. The real circuit cannot conduct a whole output.

After adding the comparator the output started to be controllable.We will check problems next week